1. Field of the Invention
The present invention relates to a noncontact tag and to a method for producing the same. More particularly, the present invention relates to a noncontact tag having an IC chip that is protected from external forces by being positioned in a space between two strip members that are placed in parallel on both sides of the IC chip, and to a method for producing the noncontact tag.
Although the noncontact IC tag of the invention can be used as a conventional tag, it is particularly suitable for use under such circumstances that tags are susceptible to external forces, such as in transportation, physical distribution, and production processes of articles, and at construction sites.
2. Background Art
Noncontact IC tags have come to be used widely as identification media in the fields of transportation, physical distribution, etc., or for such purposes as quality control, stock control, etc. because information can be recorded and stored in them and the stored information is exchangeable by communication with external devices without bringing them into contact with the devices.
However, when noncontact IC tags are used as labels in the field of physical distribution, they are often unavoidably stressed externally. If the IC chip portions of the noncontact IC tags undergo impacts, their damage is fatal. Various structures effective for protection of IC chip portions have been proposed so far. However, they are so complicated that they make it difficult to produce noncontact IC tags inexpensively.
There have been demands for noncontact IC tags having flat (plane) surfaces. It is however not easy to produce such noncontact IC tags.
An unavoidable structural problem with noncontact IC tags is that IC chips are much greater than base films, etc. in thickness. Although IC chips have been made smaller in size and thickness, the presently used IC chips are still 0.2 to 2 millimeters square in plane size and 100 to 500 μm in thickness. Therefore, even if an IC tag label is produced by connecting an IC chip to an antenna pattern formed on a base film and covering them with a surface-protective member to flatten the label surface, when a large number of the IC tag labels obtained in this manner are piled up, the total thickness of the IC chip portions becomes greater than that of the other portions of the IC tag labels.
IC chips are damaged when IC tags are piled up. Several to more than ten noncontact IC tag labels are often piled up before use, and it is common practice, for easy handling, to put one label over another in the same direction. If the labels are so piled up, the IC chip portions of the labels are inevitably brought into such a state that one IC chip portion lies on top of another. If a heavy object is put on top of the pile of the labels, the IC chips impact against one another, and silicon crystals constituting the IC chips are broken. The noncontact IC tag labels with the IC chips damaged in this manner are regarded as defective even if they are unused. Another cause of the failure of IC chips is collision of IC tags attached to rigid objects with other rigid objects. Also in this case, the IC chip portions projecting from the tag surfaces are susceptible to impact.
Although the causes of the failure of IC chips are not limited to the above-described ones, it is considered to be true that thick IC chips tend to be damaged when they are brought into contact with or collide with rigid materials such as metals.
An embodiment of a conventional noncontact IC tag is shown in FIG. 6 for reference.
A noncontact IC tag 1 comprises a base film 11, an antenna pattern 2 formed on the base film 11, and an IC chip 3 connected to both ends 2a, 2b of the antenna pattern 2 in the form of a coil. The noncontact IC tag 1 shown in FIG. 6 is one which the antenna pattern 2 in the form of a coil is formed by photo-etching metal foil that has been laminated to a transparent base film 11. FIG. 6 shows the noncontact IC tag 1 as viewed from the side that will be directed to an adherend. One end of the antenna pattern 2 is connected, with a caulker or the like, to a conducting circuit 17 penetrating into the back surface of the base film, thereby connecting both ends 2a, 2b of the antenna coil of the antenna pattern 2. The IC chip 3 is connected to both ends 2a, 2b by fixing its pad to the ends with an electrically conductive adhesive or the like. Although not shown in the figure, a pattern for thickness adjustment may also be formed around the IC chip 3. However, the thickness of the metal foil for the antenna is about 20 to 35 μm, and the total thickness of the metal foil and the pattern for thickness adjustment cannot become equal to the thickness of the IC chip 3.
The following Patent Documents 1 and 2 concern noncontact IC cards (smart cards) that belong to the technical field to which noncontact IC tags belong. The subject matters of these patents are to make IC cards uniform in thickness to make their surfaces flat. An attempt has been made to flatten not only IC cards but also noncontact IC tags, but it is confronted with a problem that the range of material choice is limited because low prices are desirable for noncontact IC tags. Further, even if IC tags are made as flat as possible, it is impossible to completely prevent IC chips from being damaged. Patent Document 3 relates to a method for producing an IC tag label, and the subject matter of the patent is to obtain a flat (plane) IC tag label. The subject matter of Patent 4 is the same as that of the present application. Patent 4 is different from the present application in that a protective member with a cavity is placed only around an IC chip.
Patent Document 1: Japanese Laid-Open Patent Publication No. 266767/1995,
Patent Document 2: Japanese Laid-Open Patent Publication No. 194801/1996,
Patent Document 3: Japanese Laid-Open Patent Publication No. 67708/2003, and
Patent Document 4: Japanese Patent Application No. 051036/2005.
The method of making thickness uniform, conventionally adopted in IC cards, is disadvantageous from the viewpoint of reduction in production cost and of material choice. Further, some difficulties have been found in the actual production process of the noncontact IC tag proposed in the above Patent Document 4.